They would need to learn a email client. The patch is in their email inbox and they don't have an easy way of applying it to their git Repository. Aerc or Mutt is necessary to accept patches easily usually, but then you have to learn those tools.

If you just copy paste into most email clients they somehow screw up the patch.

Messaging is very simple, but made hard so that the benefit is not on your side. Business opportunities, yay!